We propose to investigate further the possible relationship of EBV and of infectious mononucleosis (I.M.) to Hodgkin's disease (H.D.) in young adults. This will be done by 1) Testing sera obtained prior to the diagnosis of HD for EBV antibody levels to determine if high titers precede tumor development, 2) Compare the EBV antibody response in clinical vs. subclinical infections and in healthy adults using existing serum collections and try to assess the subsequent risk of lymphomas in the persons tested, 3) Compare in detail the epidemiological factors of HD patients, 4) Search for EBV and heterophile antigens in tissues of HD patients.